The paper develops a variant of the economic model of crime. The model developed is estimated using information on the post-release activities of a sample of men released from the North Carolina prison system. Both the expected certainty and severity of punishment are found to deter criminal activity in a number of instances and a 1 percent increase in certainty is generally found to have a greater effect than a similar increase in severity. Certainty of punishment is found to have a greater effect for relatively minor offenders and severity for persons offenders. While higher legal wages are found to deter, their effect is quite weak.